Plastic welding devices with a preheating arrangement normally comprise a housing with a lower tool arranged in it as well as an upper tool arranged in it. The lower tool is fastened on a lifting table, whereas the upper tool is fastened rigidly on an upper tool plate. By means of the lifting table, the lower tool can be moved in the direction of the upper tool in order to weld a first component in the lower tool with a second component in the upper tool, for example by means of friction welding. With the preheating arrangement, the first and the second component can normally be heated before the welding. The preheating arrangement is generally hereby coupled to the lifting table.
Such plastic welding devices are used for example in the automobile industry or in medical technology. In the automobile industry, such plastic welding devices are used for producing headlights, but can also be used in the production of other components or component groups that are made of plastics or contain plastics. Similarly, the plastic welding device can be used in the production of devices and/or component groups in medical technology or in the production of consumer goods.
The workflow for the known plastic welding device with a preheating arrangement is as follows. An operator first places a first component into the receiver of the lower tool. He then positions a second component on the first component in the lower tool. The lifting table with the lower tool and the components arranged on it then moves out of a starting position in the direction of the upper tool until the second component rests in the upper tool. The lifting table now moves back into a position, in which the preheating arrangement can be arranged from an idle position in an aligning position between the two components. After the preheating arrangement has been arranged between the two components, the preheating arrangement is positioned in a preheating position through a movement of the lifting table so that the two components are heatable at the points to be welded. After the heating, the preheating arrangement is moved back into the aligning position and then into the idle position. The lifting table is then moved into a welding position. A welding of the first component with the second component now takes place by means of friction welding or by means of the pressing together of the preheated components. After welding is complete, the lifting table with the lower tool and the compound made up of the first and second component arranged in it moves from the welding position back into the starting position. The operator can now remove the compound made up of the first and second component.
A disadvantage of the plastic welding device with a preheating arrangement described above is apparent when components with complex projections or undercuts need to be heated and welded. Since the plastic preheating arrangement is only moved in the vertical position after the aligning position has been reached, the attempt to heat such a component would lead to damage to or destruction of the component and/or of the preheating arrangement. This problem exists analogously for the lower tool. In the field of friction welding, the company BRANSON thus developed a plastic welding device, the lower tool of which can be moved on the lifting table in the space in any manner, in particular along a control line. A movement of the upper tool is not possible due to the forces occurring during the vibration welding or friction welding.
In fact, this plastic friction welding device does not have a preheating arrangement. The arrangement of a conventional preheating arrangement on the lifting table would furthermore only lead to a vertical movement of the preheating arrangement. This also means that damage to or destruction of the projections or undercuts of the component and/or of the preheating arrangement would continue to take place for components with complex projections or undercuts. Moreover, a conventional preheating arrangement is not easily integratable there since, in particular in the case of welding with prior preheating, fast mobility of the preheating arrangement and the lifting table is required. If this fast mobility does not exist, then the plastic is hardened again during welding. However, this would neither lead to the desired cosmetic weld seam nor reduced fluff formation.
One object that may be achieved by at least some implementations of the present invention is thus to provide a plastic preheating arrangement, with which even components with complex undercuts can be preheated. Furthermore, a corresponding plastic welding device as well as a preheating method are provided.